1. Field of the Invention
This invention relates to compounds which inhibit leukocyte adhesion and, in particular, leukocyte adhesion mediated by α4 integrins, where the α4 integrin is preferably VLA-4. This invention also relates to pharmaceutical compositions comprising such compounds as well as methods for treating, e.g., inflammation, using either the compounds or the pharmaceutical compositions of this invention.
2. References
The following publications are cited in this application as superscript numbers:                1 Hemler and Takada, European Patent Application Publication No. 330,506, published Aug. 30, 1989        2 Elices, et al., Cell, 60:577 584 (1990)        3 Springer, Nature, 346:425 434 (1990)        4 Osborn, Cell, 62:3 6 (1990)        5 Vedder, et al., Surgery, 106:509 (1989)        6 Pretolani, et al., J. Exp. Med., 180:795 (1994)        7 Abraham, et al., J. Clin. Invest., 93:776 (1994)        8 Mulligan, et al., J. Immunology, 150:2407 (1993)        9 Cybulsky, et al., Science, 251:788 (1991)        10 Li, et al., Arterioscler. Thromb., 13:197 (1993)        11 Sasseville, et al., Am. J. Path., 144:27 (1994)        12 Yang, et al., Proc. Nat. Acad. Science (USA), 90:10494 (1993)        13 Burkly, et al., Diabetes, 43:529 (1994)        14 Baron, et al., J. Clin. Invest., 93:1700 (1994)        15 Hamann, et al., J. Immunology, 152:3238 (1994)        16 Yednock, et al., Nature, 356:63 (1992)        17 Baron, et al., J. Exp. Med., 177:57 (1993)        18 van Dinther-Janssen, et al., J. Immunology, 147:4207 (1991)        19 van Dinther-Janssen, et al., Annals. Rheumatic Dis., 52:672 (1993)        20 Elices, et al., J. Clin. Invest., 93:405 (1994)        21 Postigo, et al., J. Clin. Invest., 89:1445 (1991)        22 Paul, et al., Transpl. Proceed., 25:813 (1993)        23 Okarhara, et al., Can. Res., 54:3233 (1994)        24 Paavonen, et al., Int. J. Can., 58:298 (1994)        25 Schadendorf, et al., J. Path., 170:429 (1993)        26 Bao, et al., Diff., 52:239 (1993)        27 Lauri, et al., British J. Cancer, 68:862 (1993)        28 Kawaguchi, et al., Japanese J. Cancer Res., 83:1304 (1992)        29 Konradi, et al., PCT/US00/01686, filed, Jan. 21, 2000.        
All of the above publications are herein incorporated by reference in their entirety to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference in its entirety.
State of the Art
VLA-4 (also referred to as α4β1 integrin and CD49d/CD29), first identified by Hemler and Takada,1 is a member of the β1 integrin family of cell surface receptors, each of which comprises two subunits, an α chain and a β chain. VLA-4 contains an α4 chain and a β1 chain. There are at least nine β1 integrins, all sharing the same β1 chain and each having a distinct a chain. These nine receptors all bind a different complement of the various cell matrix molecules, such as fibronectin, laminin, and collagen. VLA-4, for example, binds to fibronectin. VLA-4 also binds non-matrix molecules that are expressed by endothelial and other cells. These non-matrix molecules include VCAM-1, which is expressed on cytokine-activated human umbilical vein endothelial cells in culture. Distinct epitopes of VLA-4 are responsible for the fibronectin and VCAM-1 binding activities and each activity has been shown to be inhibited independently.2 
Intercellular adhesion mediated by VLA-4 and other cell surface receptors is associated with a number of inflammatory responses. At the site of an injury or other inflammatory stimulus, activated vascular endothelial cells express molecules that are adhesive for leukocytes. The mechanics of leukocyte adhesion to endothelial cells involves, in part, the recognition and binding of cell surface receptors on leukocytes to the corresponding cell surface molecules on endothelial cells. Once bound, the leukocytes migrate across the blood vessel wall to enter the injured site and release chemical mediators to combat infection. For reviews of adhesion receptors of the immune system, see, for example, Springer3 and Osborn.4 
Inflammatory brain disorders, such as experimental autoimmune encephalomyelitis (EAE), multiple sclerosis (MS) and meningitis, are examples of central nervous system disorders in which the endothelium/leukocyte adhesion mechanism results in destruction to otherwise healthy brain tissue. Large numbers of leukocytes migrate across the blood brain barrier (BBB) in subjects with these inflammatory diseases. The leukocytes release toxic mediators that cause extensive tissue damage resulting in impaired nerve conduction and paralysis.
In other organ systems, tissue damage also occurs via an adhesion mechanism resulting in migration or activation of leukocytes. For example, it has been shown that the initial insult following myocardial ischemia to heart tissue can be further complicated by leukocyte entry to the injured tissue causing still further insult (Vedder, et al.).5 Other inflammatory or medical conditions mediated by an adhesion mechanism include, by way of example, asthma,6-8 Alzheimer's disease, atherosclerosis,9-10 AIDS dementia,11 diabetes12-14 (including acute juvenile onset diabetes), inflammatory bowel disease15 (including ulcerative colitis and Crohn's disease), multiple sclerosis,16-17 rheumatoid arthritis,18-21 tissue transplantation,22 tumor metastasis,23-28 meningitis, encephalitis, stroke, and other cerebral traumas, nephritis, retinitis, atopic dermatitis, psoriasis, myocardial ischemia and acute leukocyte-mediated lung injury such as that which occurs in adult respiratory distress syndrome.
Substituted aminopyrimidines, as a class, have been disclosed as inhibiting binding of VLA-4 to VCAM-1 and, accordingly, exhibit anti-inflammatory properties.29 While these compounds possess antagonist properties to such binding, other compounds possessing such properties would also be of value.